Self cleaning dielectric heater

ABSTRACT

High frequency heating apparatus including means for generating a high frequency electromagnetic field, means for exposing a material to be heated to said electromagnetic field, a barrier web or sheet between said electrode means and said material so as to collect matter expelled by the material as it is being heated, means for continuously moving the barrier so as to continuously remove the expelled matter from the apparatus, the barrier having a low dielectric loss factor so as to not consume field energy.

United States Patent Preston [451 Mar. 28, 1972 [54] SELF CLEANING DIELECTRIC HEATER [72] inventor: Mark Preston, New Ipswich, N.H.

[73] Assignee: Litton Business Systems, Inc., New York,

[22] Filed: Apr. 13, 1970 [2 1] Appl. No.: 27,615

[52] U.S.Cl ..219/l0.6l

[51] Int. Cl. ..H05b 5/00, H05b 9/06 [58] Field ofSeai-ch ..2l9/l0.61

[56] References Cited UNITED STATES PATENTS A 2,381,278 8/1945 Gregory et al. ...219/10.6l X

Brown et a1 ...2l9/l0.61 X

2,473,251 6/1949 Hsu .L ..219/l0.6l

Primary Examiner-J. V. Truhe Assistant Examiner-Hugh D. Jaeger Attorney-Norman Friedman, Stephen E. Feldman, Morris I. Pollack, Arthur T. Groeninger and Philip Furgang [57] ABSTRACT High frequency heating apparatus including means for generating a high frequency electromagnetic field, means for exposing a material to be heated to said electromagnetic field, a barrier web or sheet between said electrode means and said material so as to collect matter expelled by the material as it is being heated, means for continuously moving the barrier so as to continuously remove the expelled matter from the apparatus, the barrier having a low dielectric loss factor so as to not consume field energy.

4 Claims, 4 Drawing Figures GENERATOR DO WE/? SOURCE SHEET 1 BF 2 FIG. 1

PATENTEDMARZB me I P'ATENTfnmzs m2 3.652.816 sum 2 OF 2 FIG.3

INVENTOR MARK PRESTON V ATTORNEY SELF CLEANING DIELECTRIC HEATER BACKGROUND OF THE INVENTION The present invention relates to heating of the dielectric material by the passage of the material through a high frequency electromagnetic field.

In drying certain materials by this method, dye stuffs, waxes, oils and the like are often expelled from the material during the heating process. This is due to vapor escaping from the material being heated and entraining impregnants and coatings therewith. These impregnants and coatings are detrimental to the operation of the apparatus because they often present fire hazards, corrode critical components and insulate the conductors from cooling air.

A particular problem in this regard is encountered in the drying of latex coated fiberglass used in the tire industry. During such drying, the latex coating is expelled, resulting in the electrodes and other critical components being coated with latex. Such latex coatings cannot be removed even by the use of solvents or hard scrubbing. permanently damaged. g

I-Ieretofore, no one has made heating apparatus of the dielectric type which has been commercially suitable for the drying of fiberglass or other materials where this problem exists.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to dielectric heating apparatus wherein materials are heated by exposure to a high frequency electromagnetic field. The invention provides for the insertion of a barrier sheet or web between the electrodes and material to be heated so as to collect matter expelled from the material being heated. The barrier sheet or web is selected from a material having a dielectric loss factor of less than 0.05 so as not to consume energy and interfere with the heating operation. The barrier is preferably in web form so as to be capable of being continuously moved through the apparatus and disposed of before expelled matter builds up. Partitions are provided to overlap the edges of the barrier web so as to completely seal off the electrodes from the material being heated. The barrier material makes two passes through the apparatus to assure complete pickup of expelled matter.

DRAWINGS FIG. 1 is a side elevation showing the apparatus constructed in accordance with the present invention.

FIG. 2 is a cross section taken on line 2-2 of FIG. 1.

FIG. 3 is a cross section taken on line 3-3 ofFIG. 2. I FIG. 4 is a modification showing the use of a endless belt barrier.

DETAILED DESCRIPTION Referring to FIG. 1, a dielectric heater 1 is shown with a web or cord of material 2 to be heated being passed over roller 3, through top wall entrance slot 4, through heating chamber 5, out through bottom wall exit slot 6 and over roller 7 to a wind or further processing station.

In order to generate an RF field, a series of electrodes 8 and 9 are mounted alternately in chamber 5 and are connected by suitable conductors l and 11 respectively to a radio frequency generator 12 and to ground. a

Radio frequency generator 12 is a conventional radio frequency oscillator capable of operating in a frequency range of 50 kHz. to 3,000 MHz. and is connected to suitable power source 13 by conductors 12A and 128.

As the material 2 is being heated, moisture therein is vaporized and this vapor carries along other contaminants which are coated or impregnated therein. In order to prevent the contaminants from fouling the electrodes 8 and 9, a barrier web 14, which is wound on a roller 15, is unrolled and passed up and through slot 6, through the heating chamber between the electrodes and the material 2 being heated, then Accordingly, the apparatus is i out through slot 4 and then around rollers 16 and 17 and again back through the heating chamber 5, around roller 18 to a drive wind-up roller 19. Any conventional drive means may be utilized for driving roller 19. Any contaminant expelled by the material being dried is caught and carried off by the barrier web 14. The barrier web 14 passes through the heating chamber 5 twice thereby affording protection against contaminants accidentally passing through the outer pass of the web.

The barrier may be chosen from any number of materials provided the material has a dielectric loss factor of less than 0.05 so as not to readily heat and consume power in the electromagnetic field. It should also be capable of withstanding the heat generated in heater 1. The latter requirement will vary depending upon the particular application.

Generally, materials which have been found suitable are fiberglass cloth, silicone rubber, flame retardant paper, and cloths made from polyester and polyamide synthetic fibers such as those sold under the trademark Dacron and Nylon.

Referring to FIGS. 2 and 3, it will be noted that the electrodes 8 and 9 are completely sealed off from the material being heated. Partitions 20 and 21 include flanges 22 and 23 which are bolted to sidewalls 24 and 25 of chamber 5. Partitions 20 and 21 extend in from sidewalls 24 and 25 and terminate adjacent the edges of the barrier web 14.

Extending from and bolted to partition 20 are panels 26 and 27 which overlap the edges of the barrier web 14 as to completely seal off the electrode chamber from the expelled matter. Similar panels 28 and 29 extend from partition 21 and overlap the opposite edge of web 14. The panels 26, 27, 28 and 29, which extend in the path of radiation between the electrodes and the material being heated are also preferably formed from a material having a low dielectric loss power. Since these panels must be rigid, they may be constructed of rigid laminates of the low dielectric loss material described above. A typical construction would comprise several layers of silicon impregnated fiberglass cloth laminated under heat and pressure. I

The spacing of panels 26 and 27 and panels 27 and 28 is such that the edges of web 14 ride in contact with the surfaces of the panels so as to make certain the electrodes are sealed off.

Referring to FIG. 4, a modification of the present invention is shown wherein the barrier material comprises an endless belt 14. A brush 31 is provided so as to clean the barrier material as it passes out of the heater 1.

In the modification of FIG. 4, a special barrier material is required so as to make easy the release of the coated contaminant. Such a barrier web may comprise, for example, silicone rubber. Generally, any material having the low dielectric loss factor and coated with a conventional release coating may be used.

Although a preferred embodiment of the invention has been disclosed, it is to be understood that changes and variations may be made within the scope of the invention.

What is claimed: 1

l. A dielectric heater including a chamber, electrodes in a portion of said chamber, a barrier for sealing off said electrode portion of said chamber, said barrier including a web, means for moving said web across the face of said electrodes, said web comprised of a material having a dielectric loss factor of less than 0.05, said barrier means including means extending from the side walls of said chamber and overlapping opposite edges of said web.

2. A dielectric heater including a chamber, electrodes in a portion of said chamber, a barrier for sealing off said electrode portion of said chamber, said barrier including a web, means for moving said web across the face of said electrodes, said web comprised of a material having a dielectric loss factor of less than 0.05, means for moviiig said web in a double pass across the face of said electrodes. v

3. A dielectric heater as defined by claim 1, means for scraping contaminants from said web, said web comprising an endless belt.

4. A dieiectric heater as defined by claim 2, means for scraping contaminants from said web, said web comprising an endless belt. 

1. A dielectric heater including a chamber, electrodes in a portion of said chamber, a barrier for sealing off said electrode portion of said chamber, said barrier including a web, means for moving said web across the face of said electrodes, said web comprised of a material having a dielectric loss factor of less than 0.05, said barrier means including means extending from the side walls of said chamber and overlapping opposite edges of said web.
 2. A dielectric heater including a chamber, electrodes in a portion of said chamber, a barrier for sealing off said electrode portion of said chamber, said barrier including a web, means for moving said web across the face of said electrodes, said web comprised of a material having a dielectric loss factor of less than 0.05, means for moving said web in a double pass across the face of said electrodes.
 3. A dielectric heater as defined by claim 1, means for scraping contaminants from said web, said web comprising an endless belt.
 4. A dielectric heater as defined by claim 2, means for scraping contaminants from said web, said web comprising an endless belt. 